We investigate the excitation of quantum plasmonic states of light in graphene using end-fire and prism coupling. In order to model the excitation process quantum mechanically, we quantize the transverse-electric and transverse-magnetic surface plasmon polariton (SPP) modes in graphene. A selection of regimes are then studied that enable the excitation of SPPs by photons and we show that efficient coupling of photons to graphene SPPs is possible at the quantum level. Furthermore, we study the excitation of quantum states and their propagation under the effects of loss induced from the electronic degrees of freedom in the graphene. Here we investigate whether it is possible to protect quantum information using quantum-error correction techniques. We find that these techniques provide a robust-to-loss method for transferring quantum states of light in graphene over large distances.